1. Field of the Invention
The present invention relates to levels. More particularly, the invention relates to a lighted level operable to reflect emitted light when the level is level and to diffuse the emitted light when the level is unlevel so that a user of the level can easily determine when an object is level.
2. Description of the Prior Art
Levels are commonly used to ensure than an object, such as a beam, stud, or other building material, is level. One problem with conventional levels, however, is that an air bubble contained within the vial is difficult to see in dim light or in the dark. Additionally, a user of the level must be very close to the level so that the user may determine the location of the air bubble within the level.
Lighted or illuminated levels have been developed to solve the above-described problems. Prior art lighted levels function by providing a general light source that illuminates a vial of the level so that a user of the level can observe center markings on the vial and the air bubble contained within the vial, even in the dark. Unfortunately, merely illuminating the level suffers from several limitations. First, it still requires the user to be close to the vial in order to see the center markings. Additionally, the light provided by the light source is diffused throughout the vial and thus, provides no light concentration. Furthermore, the user is required to observe the vial from an angle that is approximately 90° to the center of the vial, since viewing from other angles creates error in leveling due to parallax, an apparent difference in the position or direction of the bubble when it is viewed from two different points. Further yet, if the level is used, for example, to level a trailer pulled by a vehicle, then a first user must drive the vehicle while a second user monitors whether the level reads level.
To remedy some of these limitations, later prior art level designs construct a cumbersome and rather expensive device that uses at least four apertures through which light is shined to determine whether an object is level. An example of such a design is disclosed in U.S. Pat. No. 4,484,393 (the '393 patent) to LaFreniere. The '393 patent discloses a traditional level, including a housing and a vial filled with a liquid to form an air bubble that marks center. A rear of the housing is provided with two slots or apertures through which a light source emits light, such that two light paths are directed through the vial. A front of the housing is also provided with two apertures. When the air bubble is centered, each light path does not interfere with the air bubble and proceeds through the vial and the two apertures in the front of the housing. However, when the air bubble is not centered, a particular light path refracts through the air bubble such that the light path does not proceed through the aperture in the housing and is thus diffused.
Unfortunately, the level disclosed in the '393 patent still suffers from several limitations. First, due to the angle at which the path of light refracts through the air bubble when it is not centered, varying amounts of light may be diffused, thus requiring a user of the level to distinguish between varying degrees of brightness. Additionally, even when the air bubble is not centered, at least one path of light will still shine through, as illustrated in FIG. 2 of the '393 patent. Therefore, not only must a user determine how bright the path of light is that is diffused, due to refraction through the air bubble, but the user must also compare the brightness of the second path of light which proceeds through one of the apertures in the front of the housing. Furthermore, the design of the '393 patent is complex and expensive to construct in that is requires a specially aligned housing, encasing a majority of the vial, to accommodate the apertures, as illustrated in FIG. 3. Further yet, as illustrated in FIG. 3, the '393 patent's design does not provide the user the option of viewing the degree to which an object may be unlevel.
Since the apertures in the front of the housing are positioned on either side of center of the vial (see FIGS. 1 and 2) and since the apertures are positioned outside a viewing window of the vial, then the user cannot view the whole air bubble unless it is exactly centered.
Accordingly, there is a need for an improved level that overcomes the limitations of the prior art. More particularly, there is a need for a reflecting lighted level that illuminates a vial, yet does not require a user to be near to the level to determine whether an object is center. Additionally, there is a need for a reflecting lighted level that concentrates the light when the level is level as opposed to merely diffusing the light irrespective of whether the level is level or unlevel. Further, there is a need for a reflecting lighted level that does not distort the perception of an air bubble within the vial due to parallax so that the user of the level may accurately view the air bubble from any angle. Furthermore, there is a need for a reflecting lighted level that concentrates light and does not require a user of the level to determine when an object is level by distinguishing between varying degrees of brightness. There is also a need for a lighted level that is small and inexpensive to construct and that provides a user the option of viewing the level in a traditional manner using center markings or viewing the level from a distance using the emitted light to guide center.